Twinno T6000 Operating Manual Download Page 12

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Overview

The hardware version number of this document is V2.0; the software version number is V5.9 and
above. This document describes the MODBUS RTU interface in details and the target object is a
software programmer.

MODBUS command structure

Data format description in this document;
Binary display, suffix B, for example: 10001B
- decimal display, without any prefix or suffix, for example: 256
Hexadecimal display, prefix 0x, for example: 0x2A
ASCII character or ASCII string display, for example: "YL0114010022"

Command Structure

The MODBUS application protocol defines the Simple Protocol Data Unit (PDU), which is
independent of the underlying communication layer.

Figure 1: MODBUS Protocol Data Unit

MODBUS protocol mapping on a specific bus or network introduces additional fields of protocol
data units. The client that initiates the MODBUS exchange creates the MODBUS PDU, and then
adds the domain to establish the correct communication PDU.

Figure 2: MODBUS architecture for serial communication

On the MODBUS serial line, the address domain contains only the slave instrument address. Tips:
The device address range is 1...247
Set the device address of the slave in the address field of the request frame sent by the host.
When the slave instrument responds, it places its instrument address in the address area of the
response frame so that the master station knows which slave is responding.
Function codes indicate the type of operation performed by the server.
CRC domain is the result of the “ redundancy check” calculation, which is executed according to
the information content.

MODBUS RTU General Information

Function Code

Data

Address Domain

Function Code

Data

CRC

MODBUS SERIAL LINE PDU

MODBUS PDU

PH Calibration

: After entering the calibration mode, the instrument displays as shown above.

The instrument automatically identifies the standard liquid, first calibrates the midpoint (example
7.00pH), then calibrates 4.01pH or 10.01pH. The corresponding mV value will be displayed on the
left side of the screen.
After the calibration is completed, the offset and slope will be displayed on the right side of the
screen.
If only two points of calibration are needed, after two points of calibration, press the

Menu

button to exit directly.
During the calibration process, Error prompt appears on the screen when the standard liquid is
wrong.
Calibration results: The slope of glass electrode (> 0.90) is qualified, and that of metal antimony
electrode (> 0.80) is qualified.

2019-01-09 12:53:17

pH / ORP

14.51 mA

SP1

SP2

SP3

235

98 %

Done

Slope:

228 mV

2019-01-09 12:53:17

pH / ORP

14.51 mA

SP1

SP2

SP3

7.00
4.01

10.01

-5 mV

170 mV

-5 mV

98 %

Done

Calibrating

Error

offset:

Slope:

PH Calibration

USA:7.00,4.01,10.01
NIST:6.86,4.01,9.18
ORP Standard Sulution
Field Calibration
Offset Adjustment
Slope Adjustment

Standard
Calibration

Field
Calibration

Calibration

Automatic identification, calibrate 7.00 first
Automatic identification, calibrate 6.86 first
235mV(Default)

Calibration of Standard Solution

Select the Standard Solution Calibration, a total of two groups: USA: 7.00, 4.01, 10.01 and NIST:
6.86, 4.01, 9.18. After the selection is completed, press the [MENU] button to return to the
measurement screen, press the

【

CAL

】

button to enter the calibration mode of the labeling

solution.
When the Standard Solution Calibration need not be modified, pressing the

【

CAL

】

key enter

theStandard Calibration mode.
If the instrument has been calibrated, press the

【

CAL